1. Field of the Invention
In one of aspects the present invention relates to a foam laminate product, more particularly such a product adapted for use in the interior of a vehicle. In another of its aspects, the present invention relates to process for the production of a foam laminate product. In a highly preferred embodiment, the present invention relates to a headliner, more particularly a vehicular headliner. In this preferred embodiment, an aspect of present invention relates to process for the production of a headliner.
2. Description of the Prior Art
Energy absorbing devices (also known as energy management devices) and structural devices are known. Such devices can take one of a variety of shapes and forms. Currently, one of the major applications for energy absorbing devices and/or structural devices is in vehicles, particularly automobiles. Such devices, when used in vehicles, would be of great convenience if they could be included in or substituted for trim panel and, indeed, are commonly referred to as trim panels.
In recent years, one particularly useful application of such energy absorbing devices and/or structural devices which has developed is in vehicular headliners. Vehicular headliners are generally known in the art. More particularly, automotive headliners are generally known in the art. In many case an automotive headliner will serve as a structural device and a device which combines both structural and energy absorbing properties.
As is known such automotive headliners are used to line the roof of the automobile. Conventionally, an automotive headliner is a laminate structure comprising, for example, a foam or other padded element having a cover material secured thereto. The cover material comprises a finished outer surface that faces the interior of the automobile and this the cover material is disposed adjacent or is comprised in the so-called A-surface of the headliner. The surface of the headliner adjacent the A-surface is the so-called B-surface. The B-surface of the headliner may or may not comprise a cover material.
Conventionally, foamed automotive headliners have made produced from isocyanate-based foams such as polyurethane foams.
When producing automotive headliners from polyurethane foams, it is conventional to utilize the so-called free-rise or slab polyurethane foams.
In a typical slab polyurethane foam production plant, the resultant foam is usually produced by dispensing a foamable composition into a trough having an open top (also known as a tunnel) and a conveyor bottom to move the composition away from the mixhead as the foam rises. Low pressure mixing is typically used and involves metering the components for foam production into a mixhead equipped with a stirrer (or other suitable agitation means) at a pressure generally less than 500 psi (usually 200-350 psi). The components are mixed in the mixhead and the foamable composition is expanded to produce polyurethane foam. As is known in the art, low pressure mixing is conventionally used to produce slabstock foam. It is known to vary the properties of the resulting foam by varying the nature and/or amount of one or more of the metered components.
Commercial slabstock polyurethane foam plants produce foam “buns” having dimensions such as 4 feet (height)×6 feet (width)×100 feet (length). Each bun is then cut into a plurality shorter length (e.g., 5 feet) buns, depending on the specifications of the particular automotive headliner being produced. The shorter length bun is then sliced into sheets of appropriate thickness (e.g., ⅛ to ½ inches). Each sheet is then covered, trimmed and secured in the automobile. It is also known in the art to subject each sheet to further processing steps such as thermoforming so to confer to the planar sheet a slightly contoured appearance which more closely assumes the shape of the roof of the automobile.
Thus, slabstock polyurethane foam conventionally used in the production of automotive headliners is known as a foam (e.g., a resilient foam) having at least one uncontoured surface (i.e., the foam is a “free-rise” foam).
U.S. Pat. Nos. 5,683,796 and 5,721,038 [both to Kornylo et al. (Kornylo)] teach a vehicular headliner made from molded polyurethane foam. The headliner taught by Kornylo purportedly comprises a substantially constant density while having central sections with a greater cross-sectional thickness than peripheral portions. The central sections must be relatively thick such that the headliner possesses acceptable sound absorbing properties while the peripheral portions must be relatively thin so as to facilitate securing of the headliner to the roof of the automobile.
International Publication Number WO 02/42119 [Zolfaghari] teaches an improvement to the headliner taught by Kornylo. Specifically, Zolfaghari teaches a vehicular headliner comprising energy management capabilities to improve vehicle occupant safety.
Regardless of the precise mode of production, it is conventional to reinforce the headliner using fibreglass, typically fibreglass mat or chopped fibreglass.
For example, if the headliner is produced from slabstock foam, it is conventional to initially form a blank comprising a foam core, an adhesive layer on one or both sides of the foam core and fibreglass mat layer or chopped fibreglass on each adhesive layer (the blank may also comprise other layers such as a trim cover and the like). The blank is then subjected to a forming operation which serves to shape the foam core and adhere the fibreglass mat layer or chopped fibreglass to each surface of the shaped foam core. Conventional forming operations include thermoforming and thermocrushing (also known as “Cold Forming”). For more detail on the production of vehicular headliners, see, for example, “Polyurethane Foam as an Integral “Core” Component of Automotive Headliner”, Dolgopolsky et al., Polyurethanes Expo '99 (1999).
Foam laminate products produced in this manner typically do not have very good sound absorption properties. Sound absorption is desirable particularly in vehicular applications of the foam laminate (e.g., a headliner). In order to deal with this problem, it has been conventional in the prior art to subject the foam laminate product to a post-production perforation step in which the surface or surfaces of the laminate product containing adhered fibreglass is pierced. In order to achieve desirable levels of sound absorption, it is necessary to effect relatively deep penetration during the preparation step which compromises the strength and stiffness properties of the laminate. This is particularly undesirable in headliner applications in the foam laminate since, in recent years, the automotive industry has been desirous of headliner components which possess energy management properties.
Thus, despite the advances made in the art, it would be highly desirable to have a method for producing a foam laminate material which result in a product having improved sound absorption properties. It would also be highly desirable if that product maintained the strength and stiffness properties currently seen for such products. It would also be highly desirable if such a product was also characterized by an improvement in peel strength of the fibreglass layer to the foam core.